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While researching Vitamin C supplements, I noticed dozens of people outraged about various companies slipping in "synthetic vitamin c" (ascorbic acid). From what I can tell this aversion might have started from a westonaprice.org article that states:

A new study adds weight to the argument that synthetic vitamin C (ascorbic acid) may not be such a good idea. An earlier study indicates that synthetic vitamin C may contribute to the formation of genotoxins that can lead to cancer (Science 2001 Jun 15;292(5524:2083-6), and other research results, presented to the American Heart Association but never published found that those taking 500 mg vitamin C per day had a greater tendency to thickening of the arteries (Los Angeles Times, March 3, 2000).

I assume the study they are referring to is Vitamin C-Induced Decomposition of Lipid Hydroperoxides to Endogenous Genotoxins, which unfortunately isn't open-access. Does this study actually claim that exclusively "synthetic vitamin c" has this negative potential? Have there been any subsequent studies that support the claim?

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  • Whether you synthesize the chemical or extract it from a fruit, surely it is the same chemical? – Jerome Viveiros Sep 1 '20 at 6:28
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    @JeromeViveiros When they're being exact, yes. In common parlance, not always. Thus the use of the term "bioidentical" increasing in the last decade or two. I don't know about C specifically, but that's common with hormones. "Synthetic C" as a term may imply a slightly different chemical. – fredsbend Sep 1 '20 at 6:40
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    @fredsbend Vitamin C (ascorbic acid) is a small molecule (C6H8O6) so the synthetic version is the exactly the same rather than similar, though note that its stereoisomer (erythorbic acid) is synthesised by a different pathway and is not the same thing. Many hormones are much larger and so provide the opportunity for biosimilar forms. – Henry Sep 1 '20 at 8:36
  • Next sentence in the article is " In clinical trials with long follow-up periods analyzed in other reviews, vitamin C supplement use had no significant effect on the risk of myocardial infarction and stroke in subjects without diabetes17" Asplund K. Antioxidant vitamins in the prevention of cardiovascular disease: a systematic review. J Intern Med.2002;251(5):372-92. – SZCZERZO KŁY Sep 1 '20 at 9:26
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    There is no "purely syntetic" vitamin C. All industrial methods of Vitamin C production start with glucose (a plant product itself) and employ bacterias for at least one step. Newer methods are entirely bacteria-based. There is no point of using "almost identical", "bioidentical" substances or other substitutes, Vitamin C itself is cheap enough to have various non-food and non-health related uses. – fraxinus Sep 1 '20 at 19:07
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In a sciencemag.org article, which was apparently about this study, they state that:

In the process of destroying free radicals, vitamin C turns into what's called a vitamin C radical. If certain metal ions are nearby, vitamin C radical can turn compounds called lipid hydroperoxides into genotoxins, which switch bases around in DNA, disrupting its delicate code. However, these metal ions are rare in human blood.

The word "synthetic" does not appear, nor do they talk about a certain form.

In a sciencedaily.com article, which was also apparently about this study, they state:

...lead author Ian Blair of the Center for Cancer Pharmacology, at the University of Pennsylvania, cautioned that the study shouldn't be interpreted as a claim that vitamin C causes cancer.

The researchers' next step is to see whether vitamin C produces significant amounts of genotoxins in intact cells, and whether they generate cancer-causing mutations.

Again the word "synthetic" does not appear, nor do they talk about a certain form.

Further, having now scanned the study, I can say that I saw no indication that they were specifically studying the effects of synthetic vitamin C, nor did I see any mention of specific forms.


Oregon State University's (Linus Pauling Institute) Micronutrient Information Center states:

Natural and synthetic L-ascorbic acid are chemically identical and there are no known differences regarding biological activities or bioavailability (186).


In conclusion, the study was apparently about how vitamin C in general interacts with certain metals; therefore, framing it as a problem exclusively associated with synthetic Vitamin C is erroneous and misleading. While at least one other study has echoed the concerns about vitamin C's interaction with certain metals, it again is not a problem exclusively associated with synthetic Vitamin C.

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  • It's quite valuable that you yourself point out that the ref given by the claimant himself seems to not supoport the argument presented in the claim. You attacked the support. But what about 'the claim' itself?`Is it true or not? Pauling Center just gives us a wholly theoretical collateral? – LangLаngС Sep 3 '20 at 22:20
  • @LangLаngС Hi. I found that in their main article on vitamin C they give a citation. I also found support for the original concern. So I guess we could say it might be true under certain conditions, but that it's equally true for non-synthetic vitamin C. – Honest Abe Sep 3 '20 at 23:57
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I have managed to gain access to the full text of the referenced article. I can't pretend to understand it fully (not being a biochemist), but the authors do not state whether the vitamin C they used in their experiments was synthetic or a plant extract, and none of the results in the paper feature a comparison of different types of vitamin C.

Therefore I can say that this paper makes no claims to support a difference between "synthetic" vitamin C and any other kind.

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  • I'm sorry, but this answer doesn't sit right with me. It's basically "I claim that I read the article and I claim that it says X" without any citation or proof. I'm well aware that you might not be able to link to a free version of the article, but as it stands, your answer doesn't include any citation. – Elmy Sep 2 '20 at 8:21
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    @Elmy I know what you mean, but short of quoting the entire paper (in violation of copyright) I can't see how to demonstrate that it does not say these things. Anyone else can verify what I have said by reading the paper (cough-sci-hub-cough). Its not like I can quote them saying "There is no difference between natural and synthetic vit C, so we aren't going to tell you which one we used". – Paul Johnson Sep 2 '20 at 8:25
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    I think a compromise here Paul is to convert this answer into a comment. I would use the auto feature, but the text of this answer exceeds the text limit for comment. Please make this into a comment and then delete the answer. – fredsbend Sep 2 '20 at 15:04
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    @fredsbend I disagree. This is a direct answer to a question asked by the OP, so it does not belong in the comments. Answering questions in comments is rightly discouraged. – Paul Johnson Sep 2 '20 at 15:12
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    @PaulJohnson What you could do is point out that specific words do not ever appear in the article in question. The phrase "vitamin C" appears 6 times. The word "cancer" appears 9 times. The word "lipid" appears 24 times. The words artificial, natural, synth[etic|esize], manufactured, and man-made all appear zero times in the article. Evidence can be provided in the form of screen shots without violating copyright.(Information obtained by downloading the full article in PDF form and searching for strings.) – barbecue Sep 3 '20 at 16:01

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